The young man charged with DWI in last week’s tragic Long Island Expressway crash that took the life of three relatives returning from a wedding with him was not drunk, a police lab test has found.

The preliminary results appear to boost claims by Luis Ramirez’s lawyer and family that he did not cause the accident, and that the only booze he had at the wedding was a good-luck champagne toast to the bride and groom.

Ramirez, 20, said debris in the roadway from a prior accident flattened the tires on his car and several others. While he had his emergency flashers on and was moving right to exit the roadway, he was struck from the rear by a fast-moving pickup truck.

All three people in the rear of Ramirez’s vehicle died instantly: his grandfather Ernesto Villavicencio, 83; his mother, Cecilia Ramirez, 40; and his sister Fiorella Ramirez, 12. Ramirez’s girlfriend, Laurie Luna, 19, remains in critical condition.

A blood sample taken from him after accident was “negative for alcohol,” a law enforcement source said. But tests for drugs were not yet complete.

The source said the investigation was now focusing on Joshua Von Blume, 22, the driver of the pickup.

Ramirez’s lawyer, Mitchell Hirsch, said the DWI arrest was made by an off-duty cop, who smelled alcohol on Ramirez and believed he was acting drunk.

At the time, Hirsch said, Ramirez was in shock and dazed from a head injury.

Hirsch said Ramirez “did everything he could” to prevent an accident – he fought to retain control of the car, he slowed down, put on his emergency flashers and tried to pull onto the right shoulder.

Ramirez’s entire family, as well as the family of his comatose girlfriend, say they’re standing behind him.

“This is just a tragic event that happened on a day that was supposed to be a wonderful, blessed event,” said the groom, John Pilato, who was driving on the LIE with his bride, Carla, after the wedding and came on the scene of carnage.

“Everyone in Luis’ family stands 100 percent behind him,” said Pilato. “We’re all trying to heal together, as a family.